The track, which surfaced Friday, is said to have been recorded by Jackson before he died in June 2009 and updated with vocals from Bieber, the website Entertainmentwise reported Sunday.
Shortly before the song was put online, Bieber tweeted, "Excited for what is to come. MJ set the bar. Not only for music but for being an entertainer and how u treat the fans. Wish he was here..."
E! Online reported it was unclear whether the song was an intended collaboration or a fan produced track.
"MJ. The greatest of all time. #fact," Bieber later tweeted.